Question 1202878
<pre>
               TenYearsAgo      Today
SuLin          L-10             L
Sister         X-10             X

Ratio         5/7               5/6
</pre>
{{{system((L-10)/(X-10)=5/7,L/X=5/6)}}}


{{{7(L-10)=5(X-10)}}}
{{{7L-70=5X-50}}}
{{{7L-5X=20}}}



{{{L/X=5/6}}}
{{{6L=5X}}}


Substitution:
{{{7L-6L=20}}}

{{{highlight(L=20)}}}-----------Su Lin now.